Label-free detection of DNA hybridization using carbon nanotube network field-effect transistors

Abstract

We report carbon nanotube network field-effect transistors (NTNFETs) that function as selective detectors of DNA immobilization and hybridization. NTNFETs with immobilized synthetic oligonucleotides have been shown to specifically recognize target DNA sequences, including H63D single-nucleotide polymorphism (SNP) discrimination in the HFE gene, responsible for hereditary hemochromatosis. The electronic responses of NTNFETs upon single-stranded DNA immobilization and subsequent DNA hybridization events were confirmed by using fluorescence-labeled oligonucleotides and then were further explored for label-free DNA detection at picomolar to micromolar concentrations. We have also observed a strong effect of DNA counterions on the electronic response, thus suggesting a charge-based mechanism of DNA detection using NTNFET devices. Implementation of label-free electronic detection assays using NTNFETs constitutes an important step toward low-cost, low-complexity, highly sensitive and accurate molecular diagnostics.hemochromatosis ͉ SNP ͉ biosensor T he development of nucleic acids diagnostics has become the subject of intense research, especially in the postgenome era. Current methods have mainly focused on optical detection using fluorescence-labeled oligonucleotides with dyes (1), quantum dots (2), or enhanced absorption of light by oligonucleotidemodified gold nanoparticles (3). On the other hand, label-free electronic methods promise to offer sensitivity, selectivity, and low cost for the detection of DNA hybridization (4). For example, microfabricated silicon field-effect sensors can monitor directly the increase in surface charge when DNA was hybridized on the sensor surface (5). Nanomaterials possess unique properties that are amenable to biosensor applications; they are one-dimensional structures that are extremely sensitive to electronic perturbations, readily functionalized with biorecognition layers, and compatible with many semiconducting manufacturing processes. Thus, one-dimensional silicon nanowires (6-8) and indium oxide nanowires (9) have shown promising performance, because their electronic conductance is more sensitive to DNA-associated charges as a result of their high surface-tovolume ratio. Using smaller nanowires with virtually all atoms on their surface, such as single-walled carbon nanotubes (SWNTs), will provide additional advantages in DNA detection. To date, there are several reports on electrochemical detection of DNA hybridization using multi-walled carbon nanotube electrodes (ref. 10 and references therein, and ref. 11). Whereas electrochemical methods rely on electrochemical behavior of the labels, measurement of direct electron transfer between SWNTs and DNA molecules paves the way for label-free DNA detection. SWNT-based field-effect transistors (12) have excellent operating characteristics (13), and they have already been explored for highly sensitive electronic detection of gases (14, 15) and biomolecules such as antibodies (16,17).Single-stranded DNA (ssDNA) has been recently demons...

Carbon Nanotubes for Electronic and Electrochemical Detection of Biomolecules

“…Since the first demonstrations of SWNT-FETs by Dekker [89] and Avouris, [90] where p-type semiconductor FET characteristics were observed for carbon nanotubes, a number of nanotube configurations have emerged for efficient detection of a variety of biomolecules, with detection limits down to picomolar (pM) range. [23,91,92] FET-based biomolecular detection has been termed as "label-free" methodology owing to the fact that it does not employ fluorescence, electrochemical, or magnetic tags. [23,92,93] In reality, the SWNTs in their FET configuration act as "channel modulation label" to sense changes in their immediate environment, as a result of specific interactions between proteins, [23] DNA oligomers, [92] and aptamers.…”

“…[23,91,92] FET-based biomolecular detection has been termed as "label-free" methodology owing to the fact that it does not employ fluorescence, electrochemical, or magnetic tags. [23,92,93] In reality, the SWNTs in their FET configuration act as "channel modulation label" to sense changes in their immediate environment, as a result of specific interactions between proteins, [23] DNA oligomers, [92] and aptamers. [94] Figure 3a illustrates basic SWNT-FET structures with respect to the number of nanotubes spanning the channel (a 2 and a 3 ), gate configurations (a 4 and a 5 ), and various amplification strategies (a 6 -a 9 ).…”

“…[23,91] Drop casting, [95] dielectrophoresis, [96] and CVD growth [23,91,92,94,[97][98][99] have been employed for the fabrication of dispersed SWNT networks, although the latter approach is gaining greater acceptance owing to the ease of attaining bundle-free structures. Microlithography [92,94,98] and electron beam (e-beam) lithography [97] are typically employed to pattern source and drain contacts, although shadow mask metal evaporation is also used. [23,91] Figure 3a 4 and a 5 illustrate the typical gate configurations for SWNT-FET biosensors.…”

“…[79] Star et al [92] have shown that the use of divalent cations results in an increase in sensitivity by three orders of magnitude for SWNT-FET DNA sensors, which is schematically illustrated in Figure 3a 9 . Table 1 summarizes recent breakthroughs in SWNT-FET biosensors with respect to their receptor, target, device configuration, detection limit, and signal amplification.…”

“…Table 1 summarizes recent breakthroughs in SWNT-FET biosensors with respect to their receptor, target, device configuration, detection limit, and signal amplification. By integrating divalent cations and large Schottky contact areas, pM detection limits for DNA hybridization [92] and antibody-antigen binding [23,91] have been achieved. Aptamers (synthetic DNA or RNA strands designed to recognize amino acids, drugs, and proteins) were utilized to detect proteins, such as thrombin [94] and immunoglobulin E. [98] Their smaller size, as compared to protein receptors, was proposed to enhance the band structure changes in SWNT channel or Schottky barrier contact upon binding of analytes.…”